[llvm] r188879 - MC: ObjectSymbolizer can now recognize external function stubs.
Ahmed Bougacha
ahmed.bougacha at gmail.com
Wed Aug 21 00:28:13 PDT 2013
Author: ab
Date: Wed Aug 21 02:28:13 2013
New Revision: 188879
URL: http://llvm.org/viewvc/llvm-project?rev=188879&view=rev
Log:
MC: ObjectSymbolizer can now recognize external function stubs.
Only implemented in the Mach-O ObjectSymbolizer.
The testcase sadly introduces a new binary.
Added:
llvm/trunk/test/Object/Inputs/trivial-executable-test.macho-x86-64 (with props)
Modified:
llvm/trunk/include/llvm/MC/MCObjectSymbolizer.h
llvm/trunk/lib/MC/MCObjectSymbolizer.cpp
llvm/trunk/test/Object/X86/objdump-disassembly-symbolic.test
Modified: llvm/trunk/include/llvm/MC/MCObjectSymbolizer.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/MC/MCObjectSymbolizer.h?rev=188879&r1=188878&r2=188879&view=diff
==============================================================================
--- llvm/trunk/include/llvm/MC/MCObjectSymbolizer.h (original)
+++ llvm/trunk/include/llvm/MC/MCObjectSymbolizer.h Wed Aug 21 02:28:13 2013
@@ -56,6 +56,11 @@ public:
int64_t Value, uint64_t Address);
/// @}
+ /// \brief Look for an external function symbol at \p Addr.
+ /// (References through the ELF PLT, Mach-O stubs, and similar).
+ /// \returns An MCExpr representing the external symbol, or 0 if not found.
+ virtual StringRef findExternalFunctionAt(uint64_t Addr);
+
/// \brief Create an object symbolizer for \p Obj.
static MCObjectSymbolizer *
createObjectSymbolizer(MCContext &Ctx, OwningPtr<MCRelocationInfo> &RelInfo,
Modified: llvm/trunk/lib/MC/MCObjectSymbolizer.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/MC/MCObjectSymbolizer.cpp?rev=188879&r1=188878&r2=188879&view=diff
==============================================================================
--- llvm/trunk/lib/MC/MCObjectSymbolizer.cpp (original)
+++ llvm/trunk/lib/MC/MCObjectSymbolizer.cpp Wed Aug 21 02:28:13 2013
@@ -26,9 +26,18 @@ using namespace object;
namespace {
class MCMachObjectSymbolizer : public MCObjectSymbolizer {
+ const MachOObjectFile *MOOF;
+ // __TEXT;__stubs support.
+ uint64_t StubsStart;
+ uint64_t StubsCount;
+ uint64_t StubSize;
+ uint64_t StubsIndSymIndex;
+
public:
MCMachObjectSymbolizer(MCContext &Ctx, OwningPtr<MCRelocationInfo> &RelInfo,
- const MachOObjectFile *MOOF) {}
+ const MachOObjectFile *MOOF);
+
+ StringRef findExternalFunctionAt(uint64_t Addr) LLVM_OVERRIDE;
void tryAddingPcLoadReferenceComment(raw_ostream &cStream,
int64_t Value,
@@ -37,6 +46,62 @@ public:
} // End unnamed namespace
+MCMachObjectSymbolizer::
+MCMachObjectSymbolizer(MCContext &Ctx, OwningPtr<MCRelocationInfo> &RelInfo,
+ const MachOObjectFile *MOOF)
+ : MCObjectSymbolizer(Ctx, RelInfo, MOOF), MOOF(MOOF),
+ StubsStart(0), StubsCount(0), StubSize(0), StubsIndSymIndex(0) {
+
+ error_code ec;
+ for (section_iterator SI = MOOF->begin_sections(), SE = MOOF->end_sections();
+ SI != SE; SI.increment(ec)) {
+ if (ec) break;
+ StringRef Name; SI->getName(Name);
+ if (Name == "__stubs") {
+ SectionRef StubsSec = *SI;
+ if (MOOF->is64Bit()) {
+ macho::Section64 S = MOOF->getSection64(StubsSec.getRawDataRefImpl());
+ StubsIndSymIndex = S.Reserved1;
+ StubSize = S.Reserved2;
+ } else {
+ macho::Section S = MOOF->getSection(StubsSec.getRawDataRefImpl());
+ StubsIndSymIndex = S.Reserved1;
+ StubSize = S.Reserved2;
+ }
+ assert(StubSize && "Mach-O stub entry size can't be zero!");
+ StubsSec.getAddress(StubsStart);
+ StubsSec.getSize(StubsCount);
+ StubsCount /= StubSize;
+ }
+ }
+}
+
+StringRef MCMachObjectSymbolizer::findExternalFunctionAt(uint64_t Addr) {
+ // FIXME: also, this can all be done at the very beginning, by iterating over
+ // all stubs and creating the calls to outside functions. Is it worth it
+ // though?
+ if (!StubSize)
+ return StringRef();
+ uint64_t StubIdx = (Addr - StubsStart) / StubSize;
+ if (StubIdx >= StubsCount)
+ return StringRef();
+
+ macho::IndirectSymbolTableEntry ISTE =
+ MOOF->getIndirectSymbolTableEntry(MOOF->getDysymtabLoadCommand(), StubIdx);
+ uint32_t SymtabIdx = ISTE.Index;
+
+ StringRef SymName;
+ symbol_iterator SI = MOOF->begin_symbols();
+ error_code ec;
+ for (uint32_t i = 0; i != SymtabIdx; ++i) {
+ SI.increment(ec);
+ }
+ SI->getName(SymName);
+ assert(SI != MOOF->end_symbols() && "Stub wasn't found in the symbol table!");
+ assert(SymName.front() == '_' && "Mach-O symbol doesn't start with '_'!");
+ return SymName.substr(1);
+}
+
void MCMachObjectSymbolizer::
tryAddingPcLoadReferenceComment(raw_ostream &cStream, int64_t Value,
uint64_t Address) {
@@ -71,6 +136,16 @@ bool MCObjectSymbolizer::
tryAddingSymbolicOperand(MCInst &MI, raw_ostream &cStream,
int64_t Value, uint64_t Address, bool IsBranch,
uint64_t Offset, uint64_t InstSize) {
+ if (IsBranch) {
+ StringRef ExtFnName = findExternalFunctionAt((uint64_t)Value);
+ if (!ExtFnName.empty()) {
+ MCSymbol *Sym = Ctx.GetOrCreateSymbol(ExtFnName);
+ const MCExpr *Expr = MCSymbolRefExpr::Create(Sym, Ctx);
+ MI.addOperand(MCOperand::CreateExpr(Expr));
+ return true;
+ }
+ }
+
if (const RelocationRef *R = findRelocationAt(Address + Offset)) {
if (const MCExpr *RelExpr = RelInfo->createExprForRelocation(*R)) {
MI.addOperand(MCOperand::CreateExpr(RelExpr));
Added: llvm/trunk/test/Object/Inputs/trivial-executable-test.macho-x86-64
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Object/Inputs/trivial-executable-test.macho-x86-64?rev=188879&view=auto
==============================================================================
Binary files llvm/trunk/test/Object/Inputs/trivial-executable-test.macho-x86-64 (added) and llvm/trunk/test/Object/Inputs/trivial-executable-test.macho-x86-64 Wed Aug 21 02:28:13 2013 differ
Propchange: llvm/trunk/test/Object/Inputs/trivial-executable-test.macho-x86-64
------------------------------------------------------------------------------
svn:executable = *
Modified: llvm/trunk/test/Object/X86/objdump-disassembly-symbolic.test
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Object/X86/objdump-disassembly-symbolic.test?rev=188879&r1=188878&r2=188879&view=diff
==============================================================================
--- llvm/trunk/test/Object/X86/objdump-disassembly-symbolic.test (original)
+++ llvm/trunk/test/Object/X86/objdump-disassembly-symbolic.test Wed Aug 21 02:28:13 2013
@@ -3,6 +3,11 @@ RUN: | FileCheck %s -check-
RUN: llvm-objdump -d -symbolize %p/../Inputs/trivial-object-test.macho-x86-64 \
RUN: | FileCheck %s -check-prefix MACHO-x86-64
+# Generate this using:
+# ld trivial-object-test.macho-x86-64 -undefined dynamic_lookup
+RUN: llvm-objdump -d -symbolize %p/../Inputs/trivial-executable-test.macho-x86-64 \
+RUN: | FileCheck %s -check-prefix MACHO-STUBS-x86-64
+
ELF-x86-64: file format ELF64-x86-64
ELF-x86-64: Disassembly of section .text:
ELF-x86-64: main:
@@ -28,3 +33,16 @@ MACHO-x86-64: 1a: e8 00 00 00 00
MACHO-x86-64: 1f: 8b 44 24 04 movl 4(%rsp), %eax
MACHO-x86-64: 23: 48 83 c4 08 addq $8, %rsp
MACHO-x86-64: 27: c3 ret
+
+MACHO-STUBS-x86-64: file format Mach-O 64-bit x86-64
+MACHO-STUBS-x86-64: Disassembly of section __TEXT,__text:
+MACHO-STUBS-x86-64: _main:
+MACHO-STUBS-x86-64: 1f90: 48 83 ec 08 subq $8, %rsp
+MACHO-STUBS-x86-64: 1f94: c7 44 24 04 00 00 00 00 movl $0, 4(%rsp)
+MACHO-STUBS-x86-64: 1f9c: 48 8d 3d 45 00 00 00 leaq 69(%rip), %rdi ## literal pool for: Hello World!
+MACHO-STUBS-x86-64: 1fa3: e8 16 00 00 00 callq puts
+MACHO-STUBS-x86-64: 1fa8: 30 c0 xorb %al, %al
+MACHO-STUBS-x86-64: 1faa: e8 09 00 00 00 callq SomeOtherFunction
+MACHO-STUBS-x86-64: 1faf: 8b 44 24 04 movl 4(%rsp), %eax
+MACHO-STUBS-x86-64: 1fb3: 48 83 c4 08 addq $8, %rsp
+MACHO-STUBS-x86-64: 1fb7: c3 ret
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